NTRU+PKE: Efficient Public-Key Encryption Schemes from the NTRU Problem
Jonghyun Kim, Korea University
Jong Hwan Park, Sangmyung University
Abstract
We propose a new NTRU-based Public-Key Encryption (PKE) scheme called , which effectively incorporates the Fujisaki-Okamoto transformation for PKE (denoted as ) to achieve chosen-ciphertext security in the Quantum Random Oracle Model (QROM). While , a first-round candidate in the NIST PQC standardization process, was proven to be chosen-ciphertext secure in the Random Oracle Model (ROM), it lacked corresponding security proofs for QROM. Our work extends the capabilities of the recent transformation, proposed by Kim and Park in 2023, by demonstrating that an -transformed scheme can serve as a sufficient foundation for applying . Specifically, we show that the -transformed scheme achieves (weak) -spreadness, an essential property for constructing an IND-CCA secure PKE scheme. Moreover, we provide the first proof of the security of in the QROM. Finally, we show that can be further optimized into a more efficient transformation, , which eliminates the need for re-encryption during decryption. By instantiating an -transformed scheme with appropriate parameterizations, we construct , which supports 256-bit message encryption. Our implementation results demonstrate that at approximately a classical 180-bit security level, is about 2 times faster than \textsc{Kyber} + AES-256-GCM in AVX2 mode.
@misc{cryptoeprint:2024/1282,
author = {Jonghyun Kim and Jong Hwan Park},
title = {{NTRU}+{PKE}: Efficient Public-Key Encryption Schemes from the {NTRU} Problem},
howpublished = {Cryptology {ePrint} Archive, Paper 2024/1282},
year = {2024},
url = {https://eprint.iacr.org/2024/1282}
}
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